A multi-tier overlay network may include a higher tier of higher-tier base stations and higher-tier mobile stations as well as a lower tier of lower-tier base stations and lower-tier mobile stations. The lower-tier base stations and mobile stations operate within the footprint of a higher-tier base station. One issue with same-frequency multi-tier overlay networks is interference caused by conflicting communications within the same frequency spectrum. Communications within the one tier may interfere with communications within another tier. Multi-tier OFDMA overlay networks use cyclic prefixes as a guard interval to, among other things, reduce interference between symbols, however, frames from one tier that arrive outside the cyclic prefix at another tier may cause asynchronous interference. Frames from one tier that arrive within the cyclic prefix at another tier may cause synchronous interference. Asynchronous interference is significantly more difficult to manage than synchronous interference.
Thus there are general needs for reducing asynchronous interference in a multi-tier OFDMA overlay network.